Professor of Geology and Petroleum Geology, University of Aberdeen

John Parnell received funding from NERC.

The University of Aberdeen provided funding as a founding partner of The Conversation UK.

A world without large mountains—the Himalayas, the Alps, the Rockies, and the Andes—is unimaginable, but they are not always part of the earth’s geography. Mountains did not begin to form extensively until 2 billion years ago, which is half of the earth's history. Now, our research reveals how primitive life played a key role in introducing them to the earth.

Although the formation of mountains is usually related to the collision of tectonic plates causing huge rocks to be pushed into the sky, our research shows that this was triggered by the abundant nutrients in the ocean 2 billion years ago, leading to the explosive life of plankton.

Mountains are not only a beautiful backdrop for entertainment, they are also vital to the way the world works, because they affect the weather, climate, freshwater distribution, and rock erosion to form arable soil.

Before there were mountains, the plate movements that reshaped the distribution of oceans and continents only occurred within a limited range. But the movement of these plates is essential for mountain building. The pressure from one plate to another—usually an oceanic plate hitting a continental plate—causes ocean rock slabs to break and stack on top of each other when pushed from behind.

Over millions of years, these rocks have piled up to form mountains, just like the Himalayas were built from ocean rocks between India and Eurasia, pushing north until the ocean disappeared and debris piled up like mountains.

We know that these mountains originally came from the ocean. They were marine fossils found on the Qinghai-Tibet Plateau at an altitude of several thousand meters. But stacking huge rock slabs on this scale requires careful lubrication, otherwise friction will prevent them. This lubricant is carbon, and when the dead plankton falls to the bottom of the sea and is buried, the carbon becomes part of the ocean rock.

Plankton has lived in our oceans for more than 3 billion years, but 2 billion years ago, when rich nutrients entered the water, their numbers surged. At the time, life was not more complicated than their single cells. But the cells have become bigger, and they contain more carbon.

When they died, they quickly sank and were buried in mud. Rocks containing unprecedented amounts of carbon were formed in the mud. The carbon was turned into graphite under the action of heat and pressure. Graphite is a good lubricant. Using graphite, locks, hinges, gears, wheels, and even zippers can be moved more easily—the same goes for rocks.

The massive amounts of graphite accumulated under the sea floor had a profound effect and lubricated the construction of the mountains. Although it has long been known that the tectonic process is lubricated, our research shows that it is the abundant carbon in the ocean that played a key role in the thickening of the crust that formed the mountains.

Since then, this process has continued, and other geological layers such as salt have also played a role, but the graphite layer 2 billion years ago is particularly slippery, and some have participated in mountain building more than once.

The Himalayas, the largest mountain range on earth, are geologically young—about 50 million years old—but rocks formed in the older oceans slide against each other to help form them. They slipped in the first few million years after they formed, and then after a long period of dormancy, they slipped again to help the rise of the Himalayas. In the distant future, they may decline again.

Long after the disappearance of human beings, those ancient plankton will continue to have an impact on the earth. Mountains built 2 billion years ago are now worn out, but we can still see their roots in places like Scotland.

Our research examined 20 mountain building cases from all over the world at that time, from Australia to China, from South America to the Arctic and northwestern Scotland, where we can see Harris, Iona and Gairloch, which accompanied the earliest mountain architecture. Formed in the earthquake. Tiree is one of the flattest places in the UK, but seabirds running on its sandy beaches pass through the foundations of huge, long-disappeared mountains.

In each of the 20 ancient mountain ranges studied, abnormal amounts of graphite were recorded. In many cases, graphite is abundant enough to be mined as a resource.

Graphite is now a hot commodity because the core battery of green technology requires it (lithium ion batteries require much more graphite than lithium). Many of the largest graphite deposits in the world were formed about 2 billion years ago. The graphite that helped us bring the mountains may once again prove vital to the planet and play a key role in protecting the planet for future generations.

Without the carbon from countless plankton cells, the distribution of tectonic plates could be very different, and we would not have the mountains as we know it. Our planet is basically shaped by life.

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